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利用MTS 815岩石力学测试系统、声发射系统、环境扫描电镜开展石膏质岩循环荷载作用下的疲劳试验,探讨循环荷载条件对其疲劳损伤特性的影响。结果表明:石膏质岩循环荷载作用下的疲劳损伤特征明显,塑性特性显著。其疲劳试验的应力–应变全过程曲线具有如下形状特征:加载曲线可分为“近线性”的弹性特征段和“呈压扁状”的塑性特征段,塑性特征段滞后效应明显,卸载曲线呈现近线性特征。循环荷载条件对石膏质岩疲劳损伤特性影响显著,疲劳试验过程的声发射信息演化规律及微观结构变化特征能够较好地揭示其疲劳损伤演化过程及宏观破裂特征:循环应力水平高、上限应力大、加载频率低,疲劳试验的应力–应变全过程曲线越饱满疏松、加卸载的滞回环面积越大,声发射信息越强烈而集中、声发射率指标越高,试样的疲劳损伤速率快,每次循环产生的塑性应变量大,微观结构越破碎,试样的疲劳寿命越短。
MTS 815 rock mechanics test system, acoustic emission system and environmental scanning electron microscope were used to carry out fatigue tests under the cyclic load of gypsum rock, and the effects of cyclic loading conditions on the fatigue damage characteristics were studied. The results show that the fatigue damage characteristics of gypsum rock under cyclic loading are obvious and the plastic properties are obvious. The stress-strain curve of the fatigue test has the following shape features: The loading curve can be divided into “near-linear” elastic feature segments and “squashed-like” plastic feature segments with obvious hysteresis effects on the plastic feature segments , Unloading curve shows near linear features. Cyclic loading conditions have a significant influence on the fatigue damage characteristics of gypsum-hosted rocks. The evolution law of AE information and the microstructural variation during fatigue test can reveal the evolution of fatigue damage and macro-fracture characteristics well: high cyclic stress and large upper stress , The loading frequency is low, the stress-strain curve of the fatigue test is more full and loose. The larger the area of the hysteresis loop is, the stronger and more concentrated the acoustic emission information is. The higher the AE index is, the faster the fatigue damage rate is. The plastic strain generated by each cycle is large, the more the microstructure is broken, the shorter the fatigue life of the sample.